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[68.48.65.54]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8ffd56c4b91sm68559686d6.19.2026.07.11.08.05.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 11 Jul 2026 08:05:58 -0700 (PDT) From: Michael Bommarito To: Trond Myklebust , Anna Schumaker Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] pnfs/blocklayout: reject zero chunk_size and volumes_count in GETDEVICEINFO Date: Sat, 11 Jul 2026 11:05:47 -0400 Message-ID: <20260711150547.2912006-1-michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit nfs4_block_decode_volume() in fs/nfs/blocklayout/dev.c decodes stripe parameters from GETDEVICEINFO XDR without checking for zero values. A malicious pNFS server returning chunk_size=0 causes a division-by- zero panic in bl_map_stripe() via div_u64(offset, dev->chunk_size). Separately, volumes_count=0 passes the existing upper-bound check and causes a second division-by-zero via div_u64_rem(chunk, dev->nr_children=0). Impact: a malicious or compromised pNFS blocklayout server can panic an affected Linux NFS client after the client mounts/uses the server and maps I/O through the poisoned blocklayout. An in-kernel parser/mapper KUnit reproducer is available privately. Reject both zero values at decode time with -EIO. Fixes: 5c83746a0cf2 ("pnfs/blocklayout: in-kernel GETDEVICEINFO XDR parsing") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Michael Bommarito --- fs/nfs/blocklayout/dev.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c index cc6327d97a91a..fc60669db3ec4 100644 --- a/fs/nfs/blocklayout/dev.c +++ b/fs/nfs/blocklayout/dev.c @@ -183,8 +183,11 @@ nfs4_block_decode_volume(struct xdr_stream *xdr, struct pnfs_block_volume *b) return -EIO; p = xdr_decode_hyper(p, &b->stripe.chunk_size); + if (!b->stripe.chunk_size) + return -EIO; b->stripe.volumes_count = be32_to_cpup(p++); - if (b->stripe.volumes_count > PNFS_BLOCK_MAX_DEVICES) { + if (!b->stripe.volumes_count || + b->stripe.volumes_count > PNFS_BLOCK_MAX_DEVICES) { dprintk("Too many volumes: %d\n", b->stripe.volumes_count); return -EIO; } -- 2.53.0